Revert "sched, perf: Use a single callback into the scheduler"
This reverts commit cb04ff9ac424 ("sched, perf: Use a single
callback into the scheduler").
Before this change was introduced, the process switch worked
like this (wrt. to perf event schedule):
schedule (prev, next)
- schedule out all perf events for prev
- switch to next
- schedule in all perf events for current (next)
After the commit, the process switch looks like:
schedule (prev, next)
- schedule out all perf events for prev
- schedule in all perf events for (next)
- switch to next
The problem is, that after we schedule perf events in, the pmu
is enabled and we can receive events even before we make the
switch to next - so "current" still being prev process (event
SAMPLE data are filled based on the value of the "current"
process).
Thats exactly what we see for test__PERF_RECORD test. We receive
SAMPLES with PID of the process that our tracee is scheduled
from.
Discussed with Peter Zijlstra:
> Bah!, yeah I guess reverting is the right thing for now. Sad
> though.
>
> So by having the two hooks we have a black-spot between them
> where we receive no events at all, this black-spot covers the
> hand-over of current and we thus don't receive the 'wrong'
> events.
>
> I rather liked we could do away with both that black-spot and
> clean up the code a little, but apparently people rely on it.
Signed-off-by: Jiri Olsa <jolsa@redhat.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: acme@redhat.com
Cc: paulus@samba.org
Cc: cjashfor@linux.vnet.ibm.com
Cc: fweisbec@gmail.com
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/20120523111302.GC1638@m.brq.redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 8adf70e..f325786 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1084,8 +1084,10 @@
extern int perf_num_counters(void);
extern const char *perf_pmu_name(void);
-extern void __perf_event_task_sched(struct task_struct *prev,
- struct task_struct *next);
+extern void __perf_event_task_sched_in(struct task_struct *prev,
+ struct task_struct *task);
+extern void __perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next);
extern int perf_event_init_task(struct task_struct *child);
extern void perf_event_exit_task(struct task_struct *child);
extern void perf_event_free_task(struct task_struct *task);
@@ -1205,13 +1207,20 @@
extern struct static_key_deferred perf_sched_events;
-static inline void perf_event_task_sched(struct task_struct *prev,
+static inline void perf_event_task_sched_in(struct task_struct *prev,
struct task_struct *task)
{
+ if (static_key_false(&perf_sched_events.key))
+ __perf_event_task_sched_in(prev, task);
+}
+
+static inline void perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next)
+{
perf_sw_event(PERF_COUNT_SW_CONTEXT_SWITCHES, 1, NULL, 0);
if (static_key_false(&perf_sched_events.key))
- __perf_event_task_sched(prev, task);
+ __perf_event_task_sched_out(prev, next);
}
extern void perf_event_mmap(struct vm_area_struct *vma);
@@ -1286,8 +1295,11 @@
extern void perf_event_task_tick(void);
#else
static inline void
-perf_event_task_sched(struct task_struct *prev,
- struct task_struct *task) { }
+perf_event_task_sched_in(struct task_struct *prev,
+ struct task_struct *task) { }
+static inline void
+perf_event_task_sched_out(struct task_struct *prev,
+ struct task_struct *next) { }
static inline int perf_event_init_task(struct task_struct *child) { return 0; }
static inline void perf_event_exit_task(struct task_struct *child) { }
static inline void perf_event_free_task(struct task_struct *task) { }